This invention relates to a method for annealing by a high energy beam, and more particularly, to a method for annealing by a high energy beam to form a large single-crystal film.
Recently, the energy of lasers has been used for annealing the defects in implanted layers of semiconductor substrates and to ensure a high density of free electrons. (Kachurin, G. A., and two others, "Annealing of Radiation Defects by Laser Radiation Pulses", Soviet Physics Semiconductors, vol. 9, No. 7, p.946, 1975). Further, methods have been proposed to recrystallize a polycrystalline film deposited on an amorphous insulator (J. F. Gibbons and K. F. Lee, "CW Laser Recrystallization of &lt;100&gt; Si on Amorphous Substrate", Appl. Phys. Lett. 34(12), June 15, 1979, American Institute of Physics, pp. 831 to 833). Other high energy beams such as electron beams and ion beams have been used for the same purposes and the methods using these beams are under investigation.
In the process of annealing for recrystallizing a polycrystalline film deposited on an insulator, high energy beams emitted from a high energy beam generator are focused through a lens system into a beam spot having a small diameter, e.g., 10 .mu.m. This is applied to the film for annealing. The energy of the beams melts the polycrystalline film, which then solidifies and forms single-crystals. Such beams, however, usually have an intensity profile of Gaussian distribution, having the energy peak in the center of the circular beam. Consequently, the application of such a standard high energy beam on a polycrystalline film would result in solidification and recrystallization occurring from the peripheral parts toward the central part of the area of the melted region, thereby causing interference between the grain boundaries growing from the peripheral parts and limiting the increase in grain size and formation of large single-crystals.